Comparison of Tolerant Ability of Mature Field Grown Tea (<i>Camellia sinensis</i> L.) Cultivars Exposed to a Drought Stress in Passara Area

The response of some selected physiological and biochemical parameters of tea (<em>Camellia sinensis</em> L.) plants to moisture stress was evaluated using field grown, mature plants, in Field Gene Bank at Passara, Sri Lanka, to identify traits that are associated with drought tolerance which could be used for cultivar screening programs. This study was carried out from July - October 2008. Known contrasting cultivars in terms of drought tolerance were selected from the existing gene bank for the measurements. Physiological and biochemical parameters were measured to study the response of tea plants to drought stress. Identification of traits was done by using cluster analysis, cultivar &times; environment interaction and drought susceptibility index. Reduction of leaf water potential up to -0.75 to -1.5 MPa at the end of the dry period indicated that the plants were exposed to a sufficient level of moisture stress. The drought tolerant cultivars maintained a high water status with substantial rate of photosynthesis as a result of osmotic adjustments, elevated total soluble sugars and also according to previous research, due to deep rooting. Drought susceptible cultivars maintained a lower water status with lower osmotic adjustment. With cluster analysis using rates of photosynthesis and transpiration, relative water content, stomatal conductance and leaf total soluble sugar content, the cultivars could be clearly grouped as tolerant and susceptible cultivars, which agreed with their tolerance level. The parameters which could be successfully incorporated into a drought screening procedure were rate of photosynthesis, stomatal conductance, transpiration rate, relative water content and total soluble sugar content. <br /><br /><strong>Key words:</strong> Cultivar differences; Drought; Physiological and biochemical responses; Tea (<em>Camellia sinensis</em> L.). <br /><br />DOI: 10.4038/tar.v22i1.2671<br /><br /><em>Tropical Agricultural Research</em> Vol. 22 (1): 66-75 (2010)<br /><br />